In particular, the instant invention is related to a method for correcting an acquired medical image of a patient having an internal body structure, said acquired image having a region of interest showing a representation of said internal body structure, said acquired image having been acquired in a medical imager having a radiation source and a radiation detector spaced from one another along an image-taking direction, and between which the patient is disposed.
In planar imaging, there always is a magnification depending on the geometry of the radiation beam emitted by the source, the mode of projection and the position of the patient and/or the position of the region of interest inside the patient. Radiologists and orthopaedists are used to make some measurements on radiographs. However, most of the time, these measurements are approximate because the clinicians do not know accurately the factor of magnification associated with the radiographs. In fact, as the radiologist technician does not know accurately the position of the patient in the depth of the beam, he cannot provide accurately the magnification factor associated with the image.
Thus, when a radiologist wants to have an accurate measurement for a specific body part of the patient, he usually puts spherical beads (or another type of landmarks) of known dimensions on the external surface of the patient, approximately close to the location of the internal body part. Correlation between the known size of the bead and the size of the image of the bead provide the magnification factor at the external surface of the patient close to the specific body part.
However, the use of landmarks shows limitations. Positioning landmarks is time consuming, and is sometimes unpleasant for the patient (these landmarks being sometimes located near intimate parts of the body). Further, the landmarks will only provide the magnification factor at the external surface of the patient, which might be far away from the internal body part, in particular, but not only, for obese patients.
For all these reasons, one strives to limit the use of landmarks for correcting the magnification factor of a medical imager.